2-Amino-2-[2-[4-(3-benzyloxyphenylthio)-2-chlorophenyl]ethyl]-1,3-propanediol hydrochloride is a compound having a substituted diaryl sulfide structure that has excellent immunosuppressive action. This compound has been reported to have effectiveness against autoimmune diseases such as rheumatoid arthritis (Patent Literature 1). One method of producing this compound has been reported in Patent Literature 2.